CN108737267B

CN108737267B - Routing algorithm based on SDN and ICN satellite network architecture

Info

Publication number: CN108737267B
Application number: CN201810501234.2A
Authority: CN
Inventors: 刘治国; 张江梅; 朱杰; 潘成胜; 刘庆利
Original assignee: Dalian University
Current assignee: Dalian University
Priority date: 2018-05-23
Filing date: 2018-05-23
Publication date: 2020-11-27
Anticipated expiration: 2038-05-23
Also published as: CN108737267A

Abstract

The invention discloses a routing algorithm based on SDN and ICN satellite network architectures, which comprises the following specific steps: dividing virtual nodes; designing an FIB and PIT table based on the virtual nodes; step three, updating an FIB table mechanism; step four, when the ground node initiates a request to the low-rail switch node, the switch node matches the request according to the flow table, and if the matching is successful, the request is directly forwarded; otherwise, the node matches the request type according to the flow table and extracts the source and destination IP addresses or the virtual node information according to the request type, and the controller executes a routing algorithm based on the virtual node. The routing efficiency of the algorithm and the aggregation performance of the controller to the request have obvious superiority.

Description

Routing algorithm based on SDN and ICN satellite network architecture

Technical Field

The invention relates to the field of satellite communication networks, in particular to a routing algorithm based on SDN and ICN satellite network architectures.

Background

Currently, human beings enter the information age, and information is called as the core driving force of the current socioeconomic development. Conventional terrestrial information equipment and transmission systems have not met the complex information needs. Compared with land information transmission, the spatial information transmission has obvious advantages in the aspects of coverage area, access speed, efficiency, real-time performance and precision. The integrated network fully utilizes the advantages of spatial information transmission and land information transmission, and can meet increasingly miscellaneous information requirements.

With the development of the heaven-earth integrated network, the multilayer satellite network routing technology becomes an urgent problem to be solved, the high running speed of the satellite nodes enables the traditional static routing algorithm not to be well applied to the satellite network, the simple software defined satellite network cannot meet the requirement of large data time transmission, and the simple information center satellite network cannot realize data return or needs to forward the nodes to have strong routing capability.

Disclosure of Invention

Aiming at the limitation of the prior art, the virtual routing algorithm based on the virtual nodes is designed, the algorithm introduces the idea of an information center into a software-defined satellite network architecture based on a satellite network architecture (SDCSN architecture for short) of SDN and ICN technologies, the satellite network management is simplified through the characteristic of SDN transfer control separation, the response speed of a network request is improved by utilizing the characteristic of ICN cache, and meanwhile, the dynamic routing of the ICN request and data return is realized through the globality of an overhead controller by taking GEO satellite nodes as SDN controllers.

The SDICSN architecture consists of a terrestrial network and a satellite network. The ground network is divided into a plurality of Autonomous regions (AS) according to the characteristics of regions and the like, each AS is managed by a Name Routing System (NRS) controller, and network state information is exchanged among the controllers through northbound interfaces. For an ICN request in a ground network, when an interest packet of a content request reaches an OpenFlow switch node, if the interest packet can be identified by a switch, the request is forwarded according to a flow table of the switch; otherwise, the forwarding path is generated by the NRS controller according to the PIT and the FIB and is issued to the corresponding switch. Whereas for conventional IP-based requests the NRS control generates forwarding paths based on the source and destination IP addresses.

In order to achieve the purpose, the technical scheme of the application is as follows: a routing algorithm based on SDN and ICN satellite network architectures is characterized by comprising the following specific steps:

dividing virtual nodes;

designing an FIB and PIT table based on the virtual nodes;

step three, updating an FIB table mechanism;

step four, when the ground node initiates a request to the low-rail switch node, the switch node matches the request according to the flow table, and if the matching is successful, the request is directly forwarded; otherwise, the node matches the request type according to the flow table and extracts the source and destination IP addresses or the virtual node information according to the request type, and the controller executes a routing algorithm based on the virtual node.

Further, the specific way of dividing the virtual nodes in the step one is as follows:

r1: selecting the initial meridian as the initial line, and taking the direction from south to north and the direction from west to east as the positive direction;

r2: dividing the earth spherical surface into 2 × N × M logical grids according to the number N of orbital planes and the number M of satellites in each orbital plane, wherein each grid is a virtual node;

r3: each virtual node is uniquely determined by the number of the top point at the lower left corner < n, and m > is greater;

r4: after the virtual node network is determined, the mark of each virtual node uniquely corresponds to one group<Longitude and latitude>Value, i.e.

Further, in the inclined orbit constellation, the right ascension points of the N orbit surfaces are uniformly distributed in a circle of 2 pi in the plane of the equator from the overhead top view of the north pole; for the Walker constellation with the parameter of i: T/N/F, the ascent point of the initial moment of the first orbital plane is assumed to be omega₁In the first orbital plane, the initial phase angle of the numbered 1 satellite node is omega_1,1Then, the rising point right ascension and the phase angle of all satellite nodes in the constellation are calculated by the following formulas:

in the formula, T is the total number of satellites on the Walker constellation; f is the phase factor.

Further, the step two of designing the FIB and the PIT table based on the virtual node specifically includes: according to the virtual node topology strategy, the satellite network is abstracted into a large exchange node, and the source node and the destination node of the ground request are fixed relative to the satellite network.

Further, a virtual node mark where a CS node is located is added to a relation record of the FIB table content and a storage node, and a virtual node mark where a port is located is added to a relation record of the PIT table content and a forwarding port; meanwhile, the FIB and the PIT table are managed by the high-track controller, and the updating of the PIT table is dynamically updated along with the arrival of the request and the return of the data.

Further, the present application also includes: and 5: after the forwarding path is generated, the controller issues the forwarding path to the related switch node, and the switch node executes the forwarding action; when the data returns, the controller generates a return path of the data object according to the PIT table, and executes caching of the content according to the cache replacement strategy and simultaneously adds records to the FIB table.

Furthermore, in step three, a mechanism combining event driving and polling is adopted to update the FIB table mechanism, specifically: in an event-driven mechanism, when request data is returned to a satellite node, a controller actively updates an FIB table; when the switch replaces a certain content due to the execution of cache replacement operation, the switch actively informs the change, and the controller updates the FIB table; in the process, if the controller initiates a polling request to a certain node, the timer is overtime and does not receive ACK, the controller considers that the node is invalid, and updates an FIB table to mark a content name record related to the FIB table as invalid; the marked record is preferentially replaced when record replacement occurs in the FIB table.

As a further step, the routing algorithm based on the virtual node is specifically: assuming that the initial processing capacity of all satellite nodes is the same and each satellite node is linked in the directions of four domains, there are:

s1: calculating maximum traffic D of virtual nodes_＜n,m＞：

S2: calculating a virtual node load factor gamma_＜n,m＞；

Wherein data (j) represents the data transmission quantity of the satellite node j in unit time;

s3: calculating link weights w_＜n,m＞The link weight reflects the data transmission capacity of the intra-orbit and inter-orbit interplanetary links;

s4: a routing matrix is defined.

As a further step, S3: calculating link weights w_＜n,m＞The method specifically comprises the following steps:

wherein the first part is the reciprocal of the transmission time from end to end of 1bit data, L_＜n,m＞The length of an interstellar link is less than n and m, and C is the speed of light for transmitting data in vacuum; the second part is the availability of interstellar links < n, m > bandwidth, s_＜n,m＞The inter-satellite link is less than n, m is more than the residual amount of the bandwidth, B is less than n of the inter-satellite link, and m is more than the maximum value of the bandwidth; and alpha is a link weight adaptive factor, the value range of the alpha is (0,1), and the controller automatically adjusts the value of alpha according to the link bandwidth utilization rate.

As a further step, S4: defining a routing matrix:

1) if v ═ v₁,o＝o₁Then the transmission path is at a virtual node coordinate < n₁,m₁> and < n₂,m₂Generated in a matrix with diagonal vertices;

2) if v ═ v₂,o＝o₁At this time, due to the characteristic of loop formation of links in the track, in the logic network, the routing matrix circularly transmits in the vertical direction, and the transmission path is still in the virtual node coordinate < n₁,m₁> and < n₂,m₂Generated in a matrix with diagonal vertices;

3) if v ═ v₁,o＝o₂When the routing matrix is transmitted circularly in the horizontal direction;

4) if v ═ v₂,o＝o₂And at the moment, the routing matrix transmits circularly in the vertical direction and the horizontal direction.

Compared with the prior art, the invention has the beneficial effects that: the algorithm generates a routing matrix through the relative position of a source node and a destination node in a satellite network, thereby reducing the complexity of routing calculation. The routing efficiency of the algorithm and the aggregation performance of the controller to the request have obvious superiority.

Drawings

FIG. 1 is a schematic diagram of virtual node partitioning;

FIG. 2 is a diagram illustrating dynamic update of FIB tables based on an event-driven and polling mechanism;

FIG. 3 is a diagram of the virtual node routing state for an adaptive ICN and IP request;

FIG. 4 is a routing matrix logic diagram;

FIG. 5 is a graph of request latency versus request times;

FIG. 6 is an illustration of a requested degree of aggregation;

FIG. 7 is a graph of request hit rate versus number of requests;

fig. 8 is an explanatory diagram of the FIB table update speed.

Detailed Description

The invention will be further explained with reference to the drawings attached to the specification. The following examples are only for illustrating the technical solutions of the present invention more clearly, and the protection scope of the present invention is not limited thereby.

Example 1

The embodiment provides a satellite network architecture based on SDN and ICN technologies, including: an application layer, a control layer and a forwarding layer; the application layer realizes the services of content caching, name resolution, message routing, safety and the like; the north interface between the application layer and the control layer realizes the deployment of the service; the control layer is in a layered distribution type, communication among controllers in the control layer is realized through east-west interfaces, and meanwhile, each controller provides an open interface to realize the programmable function of the application layer to the controller; the forwarding layer comprises a low-orbit OpenFlow-based satellite node and a ground OpenFlow switch, and the forwarding layer is used for forwarding messages according to a flow table issued by control and increasing a caching function of returned contents. Each controller, comprising: the system comprises a network topology management module, a routing management module and a content management module; the network topology management module comprises: the system comprises a link state monitoring module and a network topology management module; the route management module comprises: the system comprises a network flow management monitoring module, a name-based routing calculation module, a Forwarding Information Base (FIB) management module and a to-be-processed request table (PIT) management module; the content management module comprises a content fragment management module, a name resolver and a content cache management module; and the controller realizes the control of the forwarding equipment by using an OpenFlow protocol through a secure channel of the OpenFlow switch. In the architecture, a controller of a ground network adopts a layered distributed control mode and is divided into a plurality of autonomous regions (AS) according to regional characteristics, each autonomous region is managed by a Name Routing System (NRS) controller, network state information is exchanged between the controllers through northbound interfaces, a satellite network in the architecture adopts a double-layer orbit design, wherein 3 synchronous satellites are used AS the controllers to realize global real-time monitoring, and a Walker constellation is adopted in a low orbit to realize global coverage.

Preferably, the architecture adopts a mode of covering an IP protocol to identify the ICN request, and uses an IF (ICN-Flag) value to distinguish the request type; for ICN requests, the Options field of the IP protocol is used to carry the content name information.

Preferably, the whole satellite operation cycle is divided into a plurality of time slices; the satellite controller periodically detects the topology change condition of the satellite network; therefore, whether the data transmission path needs to be changed or not is predicted in advance, and interruption caused by the dynamic property of the satellite network is avoided when the data packet is returned.

When the ICN client side initiates a request, whether the content needs to be forwarded through a satellite network is judged according to the request content state information in the controller, so that the forwarding process of the request is tracked through a ground or high orbit controller; when the content returns, the OpenFlow node on the return path caches the content according to the cache replacement policy. When a certain satellite node on the data return path fails to cause data interruption, the direct predecessor satellite node reports error information to the controller after ACK timeout, and the controller regenerates the data return path and avoids the failed node.

The embodiment provides an SDICSN framework aiming at the problems that large data transmission delay of videos and the like in a traditional space-ground integrated network is large, satellite network control and new service deployment are complex and the like. By introducing SDN and ICN technologies, on one hand, the control of a heaven-earth integrated network is simplified by utilizing an SDN framework, and meanwhile, the efficiency of network service deployment is improved; on the other hand, the inherent request aggregation and data distribution capacity of the forwarding nodes in the network and the characteristic that the forwarding nodes have high sensitivity and selectable cache on contents are utilized, so that the overall performance of the integrated network of heaven and earth is improved.

Example 2

In this embodiment, for the design of a low-orbit constellation, two basic parameters of the constellation are an orbit number N and a number M of satellite nodes in the same orbit, so that virtual nodes can be divided. Because the parameters of the satellite network are designed in advance, after the constellation parameters are determined, the geographic position information of each virtual node is determined, namely the latitude and longitude range of each virtual node is known. As shown in fig. 1, when the partial parameters of the constellation are (5,12), the earth sphere is divided into a logical grid of 2 × 5 × 12.

Rule 1: the initial meridian is selected as the initial meridian, and the north from south to north and the west to east from west are selected as the positive directions.

Rule 2: and dividing the earth spherical surface into 2N M logical grids according to the number N of the orbital planes and the number M of the satellites in each orbital plane, wherein each grid is a virtual node.

Rule 3: each virtual node is uniquely determined by the number of the vertex at the lower left corner < n, and m > is greater than n. For example, the virtual nodes defined by the polygon ABCD area in the figure are uniquely labeled by the number of C points < n, m > < 1,3 >.

Rule 4: after the virtual node network is determined, the mark of each virtual node uniquely corresponds to one group<Longitude and latitude>Value, i.e.

In the inclined orbit constellation, the right ascension points of the N orbit surfaces are uniformly distributed in a circle of 2 pi in the plane of the equator when viewed from above the north pole. For the Walker constellation with the parameter of i: T/N/F, the ascent point of the initial moment of the first orbital plane is assumed to be omega₁In the first orbital plane, the initial phase angle of the numbered 1 satellite node is omega_1,1Then the rising point right ascension and the phase angle of all satellite nodes in the constellation can be calculated by equation (1).

After the ascension and the phase angle of the rising intersection point of the satellite node are determined, the position of the satellite node at any moment under an equator inertial coordinate system and the longitude and latitude corresponding to the position on the ground can be calculated according to the orbital parameters of the satellite node, such as the semi-long axis, the eccentricity, the orbital inclination, the amplitude angle of the near place and the like. It is easy to determine which satellite is responsible for the communication task in the virtual node area from the longitude and latitude of the virtual node and the longitude and latitude of the satellite node in rule 4.

According to the virtual node topology strategy, the satellite network is abstracted into a large exchange node, and then the source and destination nodes of the ground request can be considered to be fixed relative to the satellite network. After introducing the virtual node, as shown in table 1 and table 2, a virtual node label where the CS node is located is added to the relationship record of the FIB table content and the storage node, and a virtual node label where the port is located is added to the relationship record of the content and the forwarding port in the PIT table. Meanwhile, the FIB and the PIT table are managed by the high-track controller, and the updating of the PIT table is dynamically updated along with the arrival of the request and the return of the data;

TABLE 1

TABLE 2

And the update mechanism for the on-satellite FIB table is described as follows: the FIB table records the mapping relationship between the content cache and the cache node in the network, and is one of the key technologies for improving the response speed of the content request. Unlike the creation and maintenance of the ground FIB table, the on-satellite FIB is divided into a satellite node cache record and a ground node cache record. The former is the number of the virtual node in the FIB table, which is NULL, and the latter is the number of the virtual node where the cache content is located. For the maintenance of the cache mapping of the satellite node, the invention is realized by adopting a mechanism combining event driving and polling, and the updating process is as shown in fig. 2. In the event-driven mechanism, when the requested data is returned to the satellite node, the record of the content name must not be available in the FIB (the reason will be explained in the routing design), and the controller actively updates the FIB table. When the switch replaces some content because of performing a cache replacement operation, the switch actively advertises the change and the controller updates the FIB table. In the process, if the controller initiates a polling request to a certain node, after the timer times out and no ACK is received, the controller considers that the node is invalid, and updates the FIB table to mark the content name record related to the FIB table as invalid. The marked record is preferentially replaced when record replacement occurs in the FIB table.

Fig. 3 is a diagram of the routing state of the virtual node for the adaptive ICN and IP request. When the ground node initiates a request to the low-rail switch node, the switch node matches the request according to the flow table, and if the matching is successful, the request is directly forwarded. Otherwise, the node matches the request type according to the flow table and extracts the source and destination IP addresses or the virtual node information according to the request type, and the controller executes a routing algorithm based on the virtual node according to the information. After the forwarding path is generated, the controller issues the forwarding path to the relevant switch node, and the switch node executes the forwarding action. When the data returns, the controller generates a return path of the data object according to the PIT table, and executes caching of the content according to the cache replacement strategy and simultaneously adds records to the FIB table. It should be noted that for content cached at the satellite node, because the high-orbit controller is sensitive to the content (via the FIB table), the request for cached content at the satellite will be sent directly to the switch node by the controller. And for the content cached in the ground network, the record of the content in the FIB is not changed when the data passes through the satellite network, the data needs to be routed again when returning to the satellite node, the process is completed by the high orbit controller, and at the moment, the controller updates the FIB table. In the process of forwarding the request and the data object, the high-orbit controller detects the link state according to the time slice, so that the link congestion is solved or avoided; when a certain satellite node fails, the predecessor node of the satellite node requests control to generate a new path again after the request is overtime, but the routing does not need to start from the source node.

When ICN requests and data returns are transmitted over the satellite network, the transmission path of interest packets and data objects requires calculation by the controller according to a routing policy. According to the introduction of the virtual nodes, as shown in fig. 1, when data is transmitted between the virtual nodes < 2,5 > and < 5,3 >, because each virtual node is responsible for communication by the satellite closest to the virtual node, the path of data transmission can be converted into the calculation of the virtual node path by the calculation of the satellite node path. The cache of the requested content has two possibilities, one is that the content is cached on the ground node; the other is that the content is cached at the satellite node. In the first case, the data return path is calculated by the virtual node where the source node and the destination node are located; in the second case, the virtual node where the node is located is obtained according to the running track of the satellite node, and then the routing calculation is converted into the first case.

The conditions and definitions of the virtual route calculation are as follows:

1. it is assumed that the initial processing power of all satellite nodes is the same.

2. Each satellite node remains connected in the four-domain direction, and is assumed to not consider reverse gaps.

3. Maximum satellite node traffic S_dmax(i) The method comprises the following steps Maximum amount of data transmitted by the satellite node i per unit time.

4. Maximum traffic volume D of virtual nodes_＜n,m＞: the maximum data volume transmitted by the virtual node in unit time is the sum of the maximum traffic volumes of all satellite nodes in the same orbit.

5. Virtual node load factor gamma_＜n,m＞: sum of data transmitted through all satellite nodes of the virtual node per unit time and D_＜n,m＞The ratio of (a) to (b). Wherein data (j) represents the data transmission amount of the satellite node j in unit time.

6. Link weight w_＜n,m＞: the link weights reflect the ability of the intra-and inter-orbital interplanetary links to transmit data. Defined by equation (4), where the first portion is the reciprocal of the end-to-end transmission time of 1bit data, L_＜n,m＞For the length of interplanetary links < n, m >, it is assumed that the data is transmitted in vacuum at the speed of light C (in units of bit m/s); the second part is the availability of interstellar links < n, m > bandwidth, s_＜n,m＞The inter-satellite link is less than n, m is more than the residual amount of the bandwidth, B is less than n of the inter-satellite link, and m is more than the maximum value of the bandwidth; and alpha is a link weight adaptive factor, the value range of the alpha is (0,1), and the controller automatically adjusts the value of alpha according to the link bandwidth utilization rate.

7. Routing matrix definition: let N be 5 and M be 7, the logical network structure of the virtual node is shown in the figure. The virtual node coordinates of the source and destination nodes returned by the data searched according to the PIT table are assumed to be < n₁,m₁> and < n₂,m₂＞。

1) If v ═ v₁,o＝o₁Then the transmission path is at a virtual node coordinate < n₁,m₁> and < n₂,m₂Generated within a matrix with diagonal vertices, such as the routing matrix in FIG. 4A-A3-B-B1.

2) If v ═ v₂,o＝o₁At this time, due to the characteristic of loop formation of links in the track, in the logic network, the routing matrix circularly transmits in the vertical direction, and the transmission path is still in the virtual node coordinate < n₁,m₁> and < n₂,m₂Generated in a matrix with diagonal vertices, such as FIG. 4, when the source and destination nodes are A, C, the routing matrix is a semi-loop matrix A-A1-C2-C1-C-C3-A2-A3.

3) If v ═ v₁,o＝o₂At this time, the routing matrix circularly transmits in the horizontal direction, and as shown in fig. 4, when the source and destination nodes are A, D, the routing matrix is a half-loop matrix a-a4-D1-D-a6-a 5.

4) If v ═ v₂,o＝o₂At this time, the routing matrix is in circular transmission in both the vertical direction and the horizontal direction, and as shown in fig. 4, when the source and destination nodes are F, E, the routing matrix is a loop matrix F-E1-E-F1.

Assuming that data is transmitted from point a to point B, an undirected graph matrix G ═ V, Y, W is obtained according to the definition of the routing matrix, where V is the set of virtual nodes, Y is the set of virtual node load rates and is determined by equation (3), and W is the set of link weights between satellite nodes responsible for virtual node communication and is determined by equation (4).

The optimal path algorithm based on the virtual routing matrix comprises the following specific implementation steps:

s1: and calculating the maximum communication volume according to the virtual node information.

S2: and calculating a routing matrix according to the node information.

S3: and calculating the load rate and the link weight matrix of the virtual nodes in the routing matrix according to the routing matrix and the traffic of the virtual nodes.

S4: and constructing an undirected graph matrix according to the information.

S5: and calculating the optimal path according to the load rate of the virtual nodes and the link weight matrix.

S6: and calculating the temporary node and the permanent node in the current working node state.

S7: and adding the working node into the path set S, ending the program if the destination node is found, and otherwise, turning to S6.

Aiming at the defects of the existing satellite network routing algorithm and the new characteristics provided by the SDICSN on the satellite network, the SDICSN provided by the embodiment provides the VDMR routing algorithm under the architecture of the SDICSN, the division rule of the ground virtual nodes is designed by utilizing the idea of virtual node topology, the satellites are numbered by utilizing the parameters of the satellite network constellation, and the one-to-one correspondence relationship between the virtual nodes and the satellite nodes is determined by the longitude and latitude of the virtual nodes and the longitude and latitude of the satellite nodes mapped to the ground. According to the operation rule of the satellite network, the virtual routing algorithm is provided, and the routing matrix is generated through the relative position of the source node and the destination node in the satellite network, so that the complexity of routing calculation is reduced.

The above description is only for the purpose of creating a preferred embodiment of the present invention, but the scope of the present invention is not limited thereto, and any person skilled in the art can substitute or change the technical solution and the inventive concept of the present invention within the technical scope of the present invention.

Claims

1. A routing method based on SDN and ICN satellite network architectures is characterized by comprising the following specific steps:

dividing virtual nodes;

designing an FIB and PIT table based on the virtual nodes;

step three, updating an FIB table mechanism;

step four, when the ground node initiates a request to the low-rail switch node, the switch node matches the request according to the flow table, and if the matching is successful, the request is directly forwarded; otherwise, the node matches the request type according to the flow table and extracts the source and destination IP addresses or the virtual node information according to the request type, and the controller executes a routing algorithm based on the virtual node;

step five: after the forwarding path is generated, the controller issues the forwarding path to the related switch node, and the switch node executes the forwarding action; when data is returned, the controller generates a return path of a data object according to the PIT table, and executes caching of content according to a caching replacement strategy and simultaneously adds records to the FIB table;

the specific way of dividing the virtual nodes in the first step is as follows:

In the inclined orbit constellation, the right ascension points of N orbit surfaces are uniformly distributed in a circle of 2 pi in the plane of the equator from the upper air of the north pole; for the Walker constellation with the parameter of i: T/N/F, the ascent point of the initial moment of the first orbital plane is assumed to be omega₁In the first orbital plane, the initial phase angle of the numbered 1 satellite node is omega_1,1Then, the rising point right ascension and the phase angle of all satellite nodes in the constellation are calculated by the following formulas:

in the formula, T is the total number of satellites on the Walker constellation; f is a phase factor;

in the second step, the FIB and PIT table are designed based on the virtual nodes, and the specific steps are as follows: abstracting the satellite network into a large exchange node according to a virtual node topology strategy, wherein a source node and a destination node of the ground request are fixed relative to the satellite network;

adding a virtual node mark where a CS node is located in a relation record of the FIB table content and a storage node, and adding a virtual node mark where a port is located in a relation record of the content and a forwarding port in a PIT table; meanwhile, the FIB and the PIT table are managed by the high-track controller, and the updating of the PIT table is dynamically updated along with the arrival of the request and the return of the data;

in the third step, a mechanism combining event driving and polling is adopted to update the FIB table, and the method specifically comprises the following steps: in an event-driven mechanism, when request data is returned to a satellite node, a controller actively updates an FIB table; when the switch replaces a certain content due to the execution of cache replacement operation, the switch actively informs the change, and the controller updates the FIB table; in the process, if the controller initiates a polling request to a certain node, the timer is overtime and does not receive ACK, the controller considers that the node is invalid, and updates an FIB table to mark a content name record related to the FIB table as invalid; when record replacement occurs in the FIB table, the marked record is replaced preferentially;

the routing algorithm based on the virtual nodes is specifically as follows: assuming that the initial processing capacity of all satellite nodes is the same and each satellite node is linked in the directions of four domains, there are:

s1: computing maximum of virtual nodeTraffic volume D_＜n,m＞：

S2: calculating a virtual node load factor gamma_＜n,m＞；

s4: defining a routing matrix;

in which the link weight w is calculated in S3_＜n,m＞The method specifically comprises the following steps:

wherein the first part is the reciprocal of the transmission time from end to end of 1bit data, L_＜n,m＞The length of an interstellar link is less than n and m, and C is the speed of light for transmitting data in vacuum; the second part is the availability of interstellar links < n, m > bandwidth, s_＜n,m＞The inter-satellite link is less than n, m is more than the residual amount of the bandwidth, B is less than n of the inter-satellite link, and m is more than the maximum value of the bandwidth; alpha is a link weight self-adaptive factor, the value range of the alpha is (0,1), and the controller automatically adjusts the value of the alpha according to the link bandwidth utilization rate;

the routing matrix is defined in S4: